It has been reported that the king penguin male, when on land to provide for the final part of incubation, is capable of retaining food in his stomach for two weeks (Gauthier-Clerc et al., 2000). The bird itself fasts and lives off of his body reserves.
To date, no similar situation is known of a higher vertebrate storing food for multiple weeks. The state of preservation of this food is remarkable since its mass and calorific value are not modified (Gauthier-Clerc et al., 2002). These observations on the state of preservation of the food strongly suggest a control of the bacterial flora present in the stomach contents. Such control of the bacterial flora would make it possible to reduce degradation of stored food. This control could be implemented via the production of substances with antimicrobial activity.
In fact, the literature reports the existence of substances with antimicrobial activity in the gastrointestinal tract of vertebrates. A major part of these substances are of a peptide nature, notably magainins, brevinins and buforins in amphibians (Moore et al., 1991; Minn et al., 1998; Wang et al., 1998), lactoferricins and defensins (α, β) in mammals, including humans (Jones and Bevins, 1992; Zhao et al., 1999; O'Neil et al., 2000). In birds, defensins have been found in other parts of the digestive tract notably the tongue, esophagus and intestine (Zhao et al., 2001). Numerous antimicrobial peptides are, moreover, present in the surface epithelia (for review, see Schröder, 1999).